1. Field of the Invention
A subject of the present invention is a process for reduction of a carbonyl compound. More precisely, the invention relates to a process for reduction of an aldehyde and/or of a ketone.
2. Description of Related Art
Various processes exist for reduction of carbonyl compounds to alcohols. In particular, reduction of aldehydes and ketones to alcohols by a hydrogenation process, in the presence of Raney nickel, is known.
The problem that arises is that the reduction of an aldehyde or of a ketone, carried out according to the aforesaid process, is a reaction that is not stereoselective, so that a mixture of stereo-isomers is obtained. This is the case when we carry out the reduction of a substituted cyclohexanone, thus resulting in a thermodynamic mixture of the stereo-isomers.
The objective of the present invention is to provide a simple reduction process that is applicable to any carbonyl compound, and more particularly to carbonyl compounds for which it is required to obtain a majority stereo-isomer.
Furthermore, Van Bekkum et al. have described the reduction of 4-tert.-butylcyclohexanone to cis-4-tert.-butylcyclohexanol, catalysed by a BEA zeofite [J. Chem. Soc., Chem. Commun., p. 1859-60 (1995)].
Use of the said catalyst on an industrial scale poses a problem because the productivity of the catalyst is inadequate and it would be necessary to have an extremely large reactor.
The aim of the present invention is to provide a process by which the aforesaid drawbacks can be obviated.
There has now been found, and this is what constitutes a subject of the present invention, a process for reduction of a carbonyl compound to the corresponding alcohol, by reaction of the said carbonyl compound with an alcohol in the presence of a zeolite catalyst, characterized by the fact that it comprises:
mixing, in any manner whatever, the carbonyl compound and the alcohol,
passing the said mixture over a catalyst bed containing at least one zeolite,
subjecting the reaction mixture leaving the catalyst bed to recirculation over the catalyst bed, for a number of times that is sufficient to obtain the desired degree of conversion of the substrate.